1. Discussion of Prior Art
A known clamp of the type mentioned (EP-A-0 056 919) has coil springs interposed between the clamp body and the control lever. The coil springs require an axial guide rod and articulations in the spring anchoring areas. This arrangement is complicated and the springs have a large amount of travel and are therefore bulky.
The aim of the present invention is to permit the production of a disengageable clamp with a simple and compact structure, insensitive to frost and ice, so as to be able to remain on line permanently.
The clamp according to the invention is characterised in that the spring is a flexion leaf spring, which cooperates on the one hand with the control lever and on the other hand with the clamp body, the leaf spring extending substantially in the said plane or parallel to this plane and in the general direction of the clamp body, and supplying the force for coupling the clamp to the cable.
A leaf spring can be housed in a restricted space and there is no risk of it being blocked by ice, the latter breaking under the least flexion of the spring. The absence of a guide rod also reduces the risk of blocking. The leaf of the spring can have, at rest, various shapes and, through a judicious choice of the anchoring points and/or of the configuration and structure of the leaf, it is easy to obtain a suitable curve for the variation in the clamp control force. The spring can be of a well known type with several leaves placed one on top of the other, with different characteristics.
The document WO-A-87 01081 and the document DE-B-10 80 580 disclose clamps incorporating a leaf spring, but this spring does not supply the force for coupling to the cable, which is derived from the weight of the car.
2. General Discussion of the Invention
According to a development of the invention, two springs are disposed symmetrically on each side of the plane containing the clamp body and control lever, so as to ensure the security of coupling of the clamp to the cable in the event of breakage of one of the springs and so as to distribute the forces.
According to one embodiment of the invention, the spring leaf, of elongate shape, is interposed between the clamp body and the control lever, one of the ends being, for example, anchored rigidly to the clamp body, on the same side as the vice, and the other end cooperating with a roller carried by the control lever, on the same side as the free end of the latter. The leaf thus extends almost parallel to the control lever and releases the space around the clamp body in the suspension member articulation area.
According to a variant embodiment, the leaf spring is almost straight, in the position of clamping the clamp, and is fixed at both ends, so as to be subjected to a buckling force during the opening movement of the clamp. The opening control is exerted on the control lever, in the usual fashion, or preferably directly on the spring.
According to another embodiment, the leaf spring has an appreciable curvature, for example in the form of a half loop or several loops in a drum shape, with a view to increasing the length of the leaf whilst limiting the bulk.
The ends of the spring leaf can be anchored rigidly, for example by embedding, on the clamp body and/or on the control lever, or can have an articulation allowing a limited relative movement.
According to another embodiment of the invention, the leaf spring is buttressed by its ends on the clamp body and its middle part cooperates with the control lever, a reverse arrangement being possible. One of the ends of the spring is, for example, embedded on the clamp body, whilst the opposite end is mounted for limited sliding by means of a rocker bar articulated on the clamp body. The two supports can consist of articulated rocker bars. The middle part of the spring is in abutment on a lug carried by the control lever in order to transmit the force of the spring to this lever. Two buttress springs with opposite curvatures can be associated by connecting their respective ends, the middle part of one of the springs cooperating with the control lever and that of the other spring with the clamp body. The ends of the springs are perfectly connected by articulations and, in this case, at least one of the middle parts is rigidly anchored to the clamp body and/or control lever.